HA Filter for solar viewing

[employee2-4601]

Hi folks,

I assume I'm not the only one who's excited about the transit of Mercury next month. I've got meself a solar filter, but was looking at getting an HA filter to enhance the view (recommended by Sky at Night mag). However, the only one I can find is the Baader HA Filter for at least a couple of hundred quid. Can anyone recommend a more bank balance-friendly option?

(Also, feel free to mention if I'm barking up the wrong proverbial...)

[Davey-T]

The HA narrowband filters are for narrow band imaging of deep sky objects.

I have one of these ( see link ) used as an energy rejection filter to cut down on the heat from the Sun, haven't tried viewing the Sun through it but don't think it would enable any HA surface detail to be seen on its own.

"Cheapest" thing is Quark eyepiece or Lunt solar scope

You should be able to get nice images with your solar filter and a DSLR

Dave

http://astrograph.net/epages/www_astrograph_net.sf/en_GB/?ObjectPath=/Shops/www_astrograph_net/Products/AGBPHA35-2

[employee2-4601]

Ah, I take it that HA Filters are designed for imaging rather than observing?

[Moonshane]

In relation to solar you cannot use the 2" Ha a filters for anything other than initial heat reduction. This is vitally important as you will possibly cause serious eye or equipment damage if you do. You need a system to include a heat reduction filter like the Baader ha plus an etalon plus a blocking filter.  The Baader filter is the cheap bit.

[employee2-4601]

I use an Astrozap filter over the scope's aperture, but I wanted something to enhance the surface detail and was given to understand that the HA Filters would do that. Methinks I've misunderstood/misread the bit in the article...

[Moonshane]

All the filters i mention above are indeed designed to gradually remove all but the very narrow ha wavelength emitted by the sun but the nasty stuff needs to be removed.

[Davey-T]

Just read the Sky at Night article and indeed it's very misleading as the pictures are all taken using HA scopes and the text is all about WL images, and a throw away line at the end.

"The king of solar filters is a hydrogen alpha filter" very misleading and potentially dangerous article IMHO.

Dave

[Moonshane]

Re the Mercury transit you won't miss too much as the transit will be visible readily in white light.

[Waldemar]

H-alpha filters for imaging or observing DSO's have a bandpass between 3 and 35 nm (1 nanometer = 1/1000,000 mm)

The smaller the bandpass, the more expensive the filter. For solar observing 0,4 - 0,6 Angstrom is normal. 1 Angstrom = 0,1 nm. So for an average, 0,05 nm would be the correct bandpass for a solarfilter... very expensive!!! Lunt, Coronado or Quark are the evidence of that.

For the transit of Mercury though, a cheap Baader solar film filter will do perfectly!

Waldemar

[employee2-4601]

OK. Much obliged folks! :-)

[Lowjiber]

That article is very misleading.  They should know better.

White light will serve you just fine.  I have a Lunt solar scope, but will likely capture it in white light.

Clear Skies

 

[Dave In Vermont]

I'll be quite content using my Thousand-Oaks solar-foil filter(which gives a orange-coloured solar-disk, compared to Baader which gives a white disk), which is tightly over the front-end of my ST80. This and I'll play with a Baader Solar-Continuum filter (which can enhance the surface-granulation) and any other filters on the eyepiece end of the telescope that I wish to try out. It's a long transit, so one will have plenty of time for experiments that beckon.

Be VERY CAREFUL, everyone! Be sure to check your filter-of-choice for any pin-holes, and other possible ways for the full-force of the solar-light to come through. And make certain the filter is well-secured to the front-end so no gusts of wind can separate it from the OTA.

Dave

 

[employee2-4601]

I've also been toying with the idea of the Solar Continuum Filter - it's one of them or a 7mm ep. Oh, decisions, decisions... :-)

[michael.h.f.wilkinson]

The Solar Continuum filter is really handy. It brings out more detail in sunspots and in particular in granulation. It is best used in a monochrome camera, although a DSLR will work fine. Note however that the image will be green. I just split the RGB image into its constituents, and only use the G band for further processing. Visually it takes a bit of getting used to, but you do get more detail

[employee2-4601]

Interesting. Might have to see if the bank balance will stretch to both...

[John]

I'll be using a Kendrick white light solar filter with my ED102 refractor. I had a trial run of this setup at the weekend and had some really nice views of the massive sunspot AR2529, granulation and some pale stringy features (faculae ?). I found 83x gave a nicely scaled view of the disk although even 166x was worth using to see more detail.

Apart from the Kendrick filter over the full aperture, I didn't use other filtration.

[Mark at Beaufort]

I think it has been explained in the previous threads that there is more to Hydrogen Alpha observing than just a filter. To get it safe there are a number of items in the telescope observing train - ERF, Etalon, Blocking filters etc and this becomes expensive.

I am hoping to observe in white light (4 inch Astro Tech APO), Herschel Wedge, Continuum Filter and binoviewers. On the other side on my SkyTee 2 mount will be my PST (Hydrogen Alpha) scope and I am hoping that Mercury will be seen against a Prom before it reaches the surface.

Well I can hope can't I

[michael.h.f.wilkinson]

I will probably set up a dual rig: The APM 80mm in white light, but with the option of switching to Ca-K, and the SolarMax-II H-alpha scope. I did work out that if I use the 2.5x PowerMate in the APM 80mm, and the 3x TeleXtender in the SolarMax-II, the scopes should be imaging at the same nominal focal length. That could be interesting when combining images. Having said that, switching around the camera will make alignment for an animation problematic, and getting another ASI174MM plus laptop for imaging is REALLY far too expensive.

[Gazabone]

There is a Coronado PST on eBay at the moment for £199. They are great scopes but, as others have said, White light is fine (I think will probably be better than Ha myself). 

[John]

With Mercury's disk being just around 12 arc seconds in apparent diameter I wonder to what extent the 40mm aperture PST would show it ?

 

[Mark at Beaufort]

9 minutes ago, John said:

With Mercury's disk being just around 12 arc seconds in apparent diameter I wonder to what extent the 40mm aperture PST would show it ?

 

John with a F/L of 400mm and using my TeleVue 8-24 zoom I am hoping to be able to see Mercury with the 50X maximum magnification. I have seen quite small sunspots on the PST and using the turnable wheel I can switch to an almost white light image to check on Mercury's movement across the disc.

[Psychobilly]

I must admit to wondering if it's going to be worth doing a WL animation... 

I was planning on using a WL solar filter on the 7D II with the 600/f4L IS USM and 1.4x Extender II  for a FL of 840mm... this gives a  full solar disc image or around 2000 pixels diameter... 1 shot every 15s for the whole period..

I was planning on using the LOHA Ha scope to image Mercury passing any features of interest on the disc.. this would mean tweaking the position to put it in the much smaller FOV... that I get with that setup... but the whole disc should still be on the 7DII's APS-c format chip... or for more wiggle room I could either drop the 1.4X extender and just image at 600mm... Or switch to the full frame (35mm)  5D III....

Peter...

 

 

[LukeSkywatcher]

I'm a bit late to the party but i was going to suggest a solar continuum filter in conjunction with the WL solar film/filter. I have a Hershel wedge (an expensive(ish) piece of kit for observing the Sun in WL). When buying the wedge its suggested to also buy a solar continuum filter because they enhance surface detail on the Sun and around sunspots. Indeed, they do. They just tweak the light coming into the scope and allow for sharper detail.

The only negative about the SC filter is that it turns the Sun a funky bright green. You soon get used to this and before long you dont even notice that you are looking at a green sun. Cant remember exactly how much i paid for my SC filter but it was the most expensive of the filters i bought. I also bought a variable polarising filter and an ND3.0 because the ND3.0 which is the main safety filter for use with the wedge was not built-in or supplied (i know.............imagine selling something that is specifically designed to observe the Sun and not supplying the one filter that will stop you from going blind).

In summary: if you want to increase detail on the Sun's surface (even when using the solar film), a SC filter is a good investment. Now i think about it mine is also the Baader SC filter and i bought it from a company in Germany and it cost about the same as the one below. 

https://www.firstlightoptics.com/solar-filters/baader-solar-continuum-filter.html

[employee2-4601]

This is my solar observation set-up. Astromaster 130EQ with a Baader Astrozap solar filter. As stated, it gives you a white light image, which is perfectly fine. However, I would like to see a little more surface detail, hence the above enquiries. With a 9mm X-Cel ep, it is possible to get quite a good view, though I'm thinking a higher mag ep might be a necessity for Mercury...

[LukeSkywatcher]

I think 9mm will be fine if you want a closer look at the tiny black dot against the surface. There wont be any detail of the planet's surface visible (i suspect that you know this already). 9mm may be a bit of a tight image and wont allow you to appreciate the bigger picture. I honestly dont know what sort of magnification to throw at the transit because ive never seen one before and Mercury is absolutely tiny against the Sun compared to Venus. That s why i'll have my 8-24mm zoom EP in place..........so i can in an instant click and zoom.

If my little 70mm scope can handle observing the Sun, then your 130mm can easily do it (as you know). The astrozap solar film gives great WL views. Buying a solar continuum filter would probably be the cheapest way to increase your observing pleasure of the Sun on any day (transit or not). It really brings out granulation on the surface and the subtle detail of factulae around sunspots.

Ive only ever seen Mercury with the naked eye on a few occasions low down just after sunset. Never seen it in a scope or bins. Ive never tried to observe it in a scope or bins.